The present invention relates to a process for extending the operating period of a circuit having MOS components exposed to gamma radiation. It more particularly applies to circuits having MOS components (metaloxide semiconductor) and specifically CMOS components (compatible MOS) for controlling and commanding robots used for interventions on nuclear sites (nuclear power stations, reprocessing plants, etc.).
Gamma radiation causes deterioration in MOS component electronic circuits, the main effect being to create electron-hole pairs. These charges can accumulate in the components and give rise to electrical arcs, which destroy the component.
Circuits especially produced for resisting different radiation types are known. The components of these circuits are produced on insulating substrates known as SOS (silicon on shire). However, these circuits, which are produced for space or military uses, are hard to obtain and their cost is roughly one hundred ties greater than that of an equivalent circuit produced in a standard technology. In addition, the range of MOS/SOS circuits is limited and often the circuits proposed have performance characteristics inferior to those of conventional circuits.
Finally, circuits produced on the basis of MOS/SOS technology have in particular been developed for resisting the latch-up effect, so as to prevent internal short-circuits resulting from pulse-type, intense gamma radiation.
In civil applications relative to the nuclear field, the circuits must be able to resist not the latch-up effect, but rather continuous gamma radiation, which is not the most harmful when it is very intense.
The guarantee of completely satisfactory operation above an accumulated gamma radiation dose threshold of 100 krad is a standard specification in civil nuclear applications. MOS circuits objective under normal conditions of use.